Method for producing highly reactive polyisobutenes

ABSTRACT

Polyisobutenes are prepared by the continuous preparation process, by polymerizing isobutene in the presence of a catalyst comprising boron trifluoride and at least one cocatalyst in an inert organic solvent, 
     a) a part of the reaction mixture obtained thereby being discharged continuously from the polymerization reactor, 
     b) the catalyst being separated from the discharge and/or being deactivated in the discharge, and 
     c) the solvent and any unconverted isobutene being separated from the discharge and recycled to the polymerization reactor, 
     wherein the recycled solvent and, if present, the isobutene are subjected to a wash with water before recycling to the polymerization reactor and are then dried.

The present invention relates to a process for the continuouspreparation of polyisobutenes by polymerizing isobutene in the presenceof a catalyst comprising boron trifluoride and at least one cocatalystin an inert organic solvent.

High molecular weight polyisobutenes having molecular weights up toseveral 100,000 Dalton have long been known. These polyisobutenes aregenerally prepared with the aid of Lewis acid catalysts, such asaluminum chloride, alkylaluminum chlorides or boron trifluoride andgenerally have not less than 10 mol % of terminal double bonds(vinylidene groups) and a molecular weight distribution (dispersity) offrom 2 to 5.

The highly reactive polyisobutenes, which as a rule have average molarmasses of from 500 to 5,000 Dalton and contain more than 60, preferablymore than 80, mol % of terminal vinylidene groups, must be distinguishedfrom these conventional polyisobutenes. In the context of the presentapplication, terminal vinylidene groups or terminal double bonds areunderstood as meaning those double bonds whose position in thepolyisobutene macromolecule is described by the formula,

where R is the polyisobutene radical shortened by two isobutene units.The type and the proportion of the double bonds present in thepolyisobutene can be determined with the aid of ¹³C-NMR spectroscopy.Such highly reactive polyisobutenes are used as intermediates for thepreparation of additives for lubricants and fuels, as described, forexample, in DE-A 27 02 604. The terminal vinylidene groups have thehighest reactivity, whereas the double bonds present further toward theinterior of the macromolecules exhibit in the usual functionalizationreactions only very little reactivity, if any at all, depending on theirposition in the macromolecule. The proportion of terminal vinylidenegroups in the molecule is therefore the most important quality criterionfor this type of polyisobutene.

Further quality criteria for polyisobutene are their average molecularweight and the molecular weight distribution (also referred to asdispersity) of the macromolecules contained in the polyisobutene. Ingeneral, polyisobutenes having average molecular weights (M_(n)) of from500 to 50,000 Dalton are desirable. Molecular weights of from 500 to5,000, preferably from 600 to 3,000, in particular from 700 to 2,500,Dalton are preferred for the preparation of polyisobutenes used as fueladditives, owing to their better efficiency.

Furthermore, a narrow molecular weight distribution of the polyisobutenemolecules is desirable in order to reduce the proportion of undesired,relatively low molecular weight or high molecular weight polyisobutenesin the product produced and thus to improve its quality.

Various polymerization reactions of isobutene under catalysis by variousboron trifluoride complexes are known.

EP 0 807 641 A2 describes a process for the preparation of highlyreactive polyisobutene having an average molecular weight of more than5,000 and up to 80,000 Dalton and containing at least 50 mol % ofterminal vinylidene groups. The cationic polymerization of isobutene orisobutene-containing hydrocarbons is carried out in the liquid phase inthe presence of boron trifluoride complex catalysts at below 0° C. andfrom 0.5 to 20 bar, in one stage at a steady-state isobuteneconcentration of from 20 to 80% by weight. The boron trifluoride complexcatalysts can be premolded before they are used or can be produced insitu in the polymerization reactor. The boron trifluoride concentrationis from 50 to 500 ppm.

EP 0 628 575 A1 describes a process for the preparation of highlyreactive polyisobutene containing more than 80 mol % of terminalvinylidene groups and having an average molecular weight of from 500 to5,000 Dalton by cationic polymerization of isobutene orisobutene-containing hydrocarbons in the liquid phase in the presence ofboron trifluoride and secondary alcohols of 3 to 20 carbon atoms. Inaddition to the separate preparation of the boron trifluoride complexwith subsequent introduction into the reaction stream, production of thecomplex in situ is also proposed. The process is preferably operatedwith establishment of a steady-state monomer concentration in thereaction medium, which as a rule is set in the range from 0.2 to 50,preferably from 0.2 to 5, % by weight, based on the total polymerizationmixture.

WO 99/31151 describes a process for the preparation of highly reactivelow molecular weight polyisobutene, in which some of the borontrifluoride complex catalyst is recovered by separating the reactordischarge into a product-rich phase and a catalyst-rich phase andrecycling the catalyst-rich phase to the polymerization reactor.However, this procedure makes it more difficult to carry out thereaction.

However, the reaction must be carried out precisely in order to ensurethe product quality, in particular the uniformity of the molecularweight (i.e. for narrow molecular weight distribution) and a highcontent of vinylidene double bonds.

It is an object of the present invention to provide a continuous processfor the preparation of polyisobutene having the generic features of thepreamble of claim 1, in which the reaction can be carried out moreprecisely.

We have found that this object is achieved by a process for thecontinuous preparation of polyisobutene by polymerizing isobutene in thepresence of a catalyst comprising boron trifluoride and at least onecocatalyst in an inert organic solvent,

a) a part of the reaction mixture obtained thereby being dischargedcontinuously from the polymerization reactor,

b) the catalyst being separated from the discharge and/or beingdeactivated in the discharge and,

c) the solvent and any unconverted isobutene being separated from thedischarge and recycled to the polymerization reactor,

wherein the recycled solvent and, if present, the isobutene aresubjected to a wash with water before the recycling to thepolymerization reactor and, if required, are then dried.

The separation of the solvent and of any unconverted isobutene from thedischarge is effected as a rule by distilling off the solvent, isobuteneand other volatile components also distilling off. As a result of thenovel washing of the solvent with water before the recycling, theresidues of water-soluble cocatalysts and traces of fluorine-containingdecomposition products still present are removed in a simple manner andwith high efficiency.

The washing of the solvent before recycling can be carried out in onestage or a plurality of stages. In a one-stage procedure, as a rule thesolvent separated from the discharge is mixed with a sufficient amountof water in a mixer and a phase separation is then carried out in aseparation vessel. For the multistage wash, these operations can berepeated several times in the manner of a cascade. Preferably, themultistage wash is carried out in an extraction column.

For washing the solvent, as a rule the solvent/water ratio of from 20:1to 1:2, in particular from 10:1 to 1:1 (v/v) is chosen. In a one-stagewash, the ratio of solvent to water is particularly preferably about 1:1(v/v); in a multistage wash or in the extraction using an extractioncolumn, the solvent/water ratio is preferably not less than 2:1 andpreferably from 2:1 to 1:10.

The wash is carried out as a rule at from 5 to 80° C., preferably from10 to 50° C. A wash under superatmospheric pressure is also suitable.

The wash water produced during washing of the solvent (and of anyunconverted isobutene) can be removed as wastewater. Since the pollutionof the wash water with residues of water-soluble cocatalyst andfluorine-containing decomposition products is comparatively low, thewash water can advantageously be reused in the novel process before itis disposed of as wastewater. The wash water is, for example, suitablefor deactivating the catalyst in the reaction discharge withsimultaneous extraction of the catalyst decomposition products from thereaction discharge, as described in more detail further below. Thissecond use of the wash water leads on the one hand to a saving of freshwater and a reduction in the amount of wastewater in the total process.A further advantage is the reduction of solvent and isobutene losses,which are attributable to the fact that the solvent and isobutene areslightly soluble in water. Since the wash water is already saturatedwith solvent (and possibly isobutene) after the washing of the recycledsolvent (and any isobutene), there is no further passage of solvent andany isobutene into the wash water phase in the catalyst deactivationstage, so that the losses of solvent and any isobutene via thewastewater are reduced.

After the solvent has been separated off, the residue which contains thedesired polyisobutene is worked up in a conventional manner. For thispurpose, the residue is subjected, for example, to further washingstages with water or alcoholic solvents, e.g. methanol, or solvent/watermixtures, in order to remove catalyst residues. Traces of solvent and ofwater as well as volatile oligomers of isobutene are removed byconventional methods, for example by evaporation in an annular gapevaporator or by extrudate devolatilization.

The novel process is a continuous process. Measures for continuouslypolymerizing isobutene in the presence of catalysts comprising borontrifluoride and at least one cocatalyst in inert organic solvents togive polyisobutene are known per se. In a continuous process, a part ofthe reaction mixture formed in the polymerization reactor is dischargedcontinuously. Of course, an amount of starting material whichcorresponds to the discharge is fed continuously to the polymerizationreactor. The ratio of the amount of substance present in thepolymerization reactor to the amount which is discharged is determinedby the circulation/feed ratio, which in the continuous polymerization ofisobutene to polyisobutene is as a rule from 1000:1 to 1:1, according tothe invention preferably from 500:1 to 5:1, in particular from 50:1 to200:1 (v/v). The average residence time of the isobutene to bepolymerized in the polymerization reactor may be from 5 seconds toseveral hours. Residence times of from 1 to 30, in particular from 2 to20, minutes are preferred. The polymerization of the isobutene iseffected in the reactors customary for the continuous polymerization,such as stirred kettles, tubular reactors, tube-bundle reactors and loopreactors, loop reactors, i.e. tube (-bundle) reactors having stirredkettle characteristics, being preferred. Tubular reactors having tubecross-sections which lead to turbulence in sections are particularlyadvantageous.

The novel process is carried out as a rule at a polymerizationtemperature of from −60° C. to +40° C., preferably below 0° C.,particularly preferably from −50° C. to −40° C., especially from −10° C.to −30° C. The heat of polymerization is correspondingly removed withthe aid of a cooling apparatus. This may be operated, for example, withliquid ammonia as coolant. Another possibility for removing the heat ofpolymerization is by evaporative cooling. The heat liberated is removedby evaporating the isobutene and/or other readily volatile components ofthe isobutene feedstock or any readily volatile solvent. The novelpolymerization process is preferably carried out under isothermalconditions, i.e. the temperature of the liquid reaction mixture in thepolymerization reactor has a constant value and changes only to a smallextent, if at all, during the operation of the reactor.

The concentration of the isobutene in the liquid reaction phase is as arule from 0.2 to 50, preferably from 0.5 to 20, in particular from 1 to10, % by weight, based on the liquid reaction phase. In the preparationof polyisobutenes having number-average molecular weights M_(n) of from500 to 5,000 Dalton, an isobutene concentration of from 1 to 20, inparticular from 1.5 to 15, % by weight is preferably employed. In thepreparation of polyisobutenes having a number-average molecular weightM_(n) above 5,000 Dalton, an isobutene concentration of from 4 to 50% byweight is preferably employed.

The isobutene conversion can in principle be established as desired.However, it is self evident that the cost-efficiency of the process isdoubtful at very low isobutene conversions whereas the danger of thedouble bond shifts increases and shorter reaction times and improvedheat removal are required at very high isobutene conversions of morethan 99%. For these reasons, the isobutene conversion is usually carriedout to values in the range from 20 to 99%. Isobutene conversions from 70to 98% are particularly preferred.

Suitable feedstocks for the novel process are isobutene itself andisobutene-containing C₄-hydrocarbon streams, for example refined C₄fractions, C₄ cuts from isobutene dehydrogenation and C₄ cuts from steamcrackers and FCC crackers (FCC: Fluid Catalysed Cracking), provided thatthey have been substantially freed from 1,3-butadiene contained therein.C₄-hydrocarbon streams suitable according to the invention contain, as arule, less than 500 ppm, preferably less than 200 ppm, of butadiene. Thepresence of 1-butene and cis- and trans-2-butene is substantiallynoncritical for the novel process and does not lead to loss ofselectivity. Typically, the concentration in the C₄-hydrocarbon streamsis from 40 to 60% by weight. When C₄-cuts are used as feedstock, thehydrocarbons other than isobutene assume the role of an inert solvent.The isobutene feedstock may contain small amounts of contaminants, suchas water, carboxylic acids or mineral acids without resulting incritical reductions in yield or in selectivity during thepolymerization. This results in lower alcohol/ether consumption, whichchanges the abovementioned molar ratios in favor of BF₃. It is expedientto avoid an accumulation of these impurities in the plant, by removingsuch pollutants, for example by adsorption on solid adsorbents, such asactive carbon, molecular sieves or ion exchangers, from theisobutene-containing feedstock.

Solvents or solvent mixtures which are suitable for the novel processare those which are inert to the reagents used. Suitable solvents are,for example, saturated hydrocarbons, such as butane, pentane, hexane,heptane or octane, e.g. n-hexane, isooctane, cyclobutane orcyclopentane, halogenated hydrocarbons, such as methyl chloride,dichloromethane or trichloromethane, and mixtures of the abovementionedcompounds. Before they are used in the novel process, the solvents arepreferably freed from impurities, such as water, carboxylic acids ormineral acids, for example by adsorption on solid adsorbents, such asactive carbon, molecular sieves or ion exchangers.

In the novel process, the polymerization is carried out in the presenceof boron trifluoride complex catalysts. These are understood as meaningcatalysts comprising boron trifluoride and at least one cocatalyst.Suitable cocatalysts are as a rule oxygen-containing compounds. Suitableoxygen-containing compounds in addition to water are organic compoundsof up to 30 carbon atoms which contain at least one oxygen atom bondedto carbon. Examples of these are C₁-C₁₀-alkanols and cycloalkanols,C₂-C₁₀-diols, C₁-C₂₀-carboxylic acids, C₄-C₁₂-carboxylic anhydrides andC₂-C₂₀-dialkyl ethers. Preferred among these are monohydric alkanols offrom 1 to 20, in particular 1 to 4, carbon atoms, which, if required,can be used together with the C₁-C₂₀-dialkyl ethers. Molar ratios ofboron trifluoride to oxygen-containing compound of from 1:1 to 1:10, inparticular from 1:1.1 to 1:5, especially from 1:1.2 to 1:2.5 arepreferred according to the invention in boron trifluoride complexcatalysts. The BF₃ concentration in the reactor will as a rule vary inthe range from 0.01 to 1, in particular from 0.02 to 0.7, especiallyfrom 0.03 to 0.5, % by weight, based on the liquid reaction phase.

In the novel process, the oxygen-containing compound in the borontrifluoride complex catalyst particularly preferably comprises at leastone monohydric, secondary alcohol A of 3 to 20 carbon atoms. Examples ofsuitable secondary alcohols are the following: isopropanol, 2-butanol,and furthermore sec-pentanols, sec-hexanols, sec-heptanols,sec-octanols, sec-nonanols, sec-decanols or sec-tridecanols. In additionto monohydric, secondary alcohols, it is also possible to use(poly)etherols of propene oxide and of butene oxide according to theinvention. 2-Butanol and in particular isopropanol are preferably used.

The boron trifluoride complexes can be preformed in separate reactorsbefore they are used in the novel process, temporarily stored on theirformation and metered into the polymerization apparatus according todemand. The BF₃ complex catalysts are prepared as a rule by passing BF₃into the cocatalyst or into a solution of the cocatalyst in one of theabovementioned inert organic solvents at from −60 to +60° C., preferablyfrom −30 to +20° C. The activity of the catalyst can be manipulated byadding further cocatalysts.

In another, preferred variant, the boron trifluoride complexes areproduced in situ in the polymerization apparatus. In this procedure, therespective cocatalyst is, if required, fed together with a solvent intothe polymerization apparatus and boron trifluoride is dispersed in therequired amount in this mixture of the reactants. Here, the borontrifluoride and the cocatalysts react to give the boron trifluoridecomplex. Instead of an additional solvent, isobutene or the reactionmixture comprising unconverted isobutene and polyisobutene can act as asolvent in the in situ production of the boron trifluoride catalystcomplex.

In a preferred embodiment, first a complex of dialkyl ether B and BF₃ isprepared separately or in the solvent feed to the reactor and onlythereafter combined with the secondary alcohol A in the complex feed orsolvent feed to the reactor or in the reactor itself. Consequently, theenergy of the complex formulation can be removed without harmfulbyproduct formation during the production of the alcohol complex.Moreover, this procedure permits the simple manipulation of the catalystactivity via the ratio of boron trifluoride to alcohol.

Gaseous boron trifluoride is expediently used as raw material for thepreparation of the boron trifluoride complexes, it being possible to usetechnical-grade boron trifluoride still containing small amounts ofsulfur dioxide and SiF₄ (purity: 96.5% by weight), but preferablyhigh-purity boron trifluoride (purity: 99.5% by weight).

The reaction mixture discharged from the polymerization reactor stillcontains a polymerizable isobutene, BF₃ and cocatalyst. As a rule, thepolymerization therefore also continues in the discharge. As a result ofthis, the polyisobutene formed in the polymerization reactor may changein a disadvantageous manner with respect to molecular weight, molecularweight distribution and terminal group content. To prevent furtherreaction, the polymerization is therefore usually stopped bydeactivating the catalyst. The deactivation can be effected, forexample, by adding water, alcohols, acetonitrile, ammonia or aqueoussolutions of mineral bases or by passing the discharge into one of theabovementioned media. The deactivation is preferably carried out usingwater, preferably at from 1 to 60° C. (water temperature). During thedeactivation with water the deactivation in the narrow sense of the word(by formation of a catalytically inactive BF₃-water complex) isaccompanied by hydrolysis of the boron trifluoride to water-solublehydrolysis products, such as boric acid and hydrogen fluoride, whichpass over into the aqueous phase and are thus removed for the most partfrom the orgaic phase. After phase separation into an organic phase andinto an aqueous phase, if required, the solvent is separated from thepolyisobutene in the discharge thus deactivated, by evaporation andcondensation or by controlled distillation, and is further treated inthe manner described above.

In a preferred embodiment of the novel process, the boron trifluoridecomplex catalyst is substantially separated from the discharge andrecycled to the polymerization reaction. The separation and recycling ofthe catalyst from the discharge of the polymerization reaction isdisclosed in WO 99/31151, which is hereby incorporated in full byreference. For separation of the catalyst from the discharge, preferablyboron trifluoride complex catalysts having limited solubility are usedand/or the reaction mixture is cooled to, for example, from 5 to 30,preferably from 10 to 20, Kelvin below the reactor temperature.

On separating the catalyst from the reactor discharge, it is advisableto reduce the isobutene concentration of the discharge to below 2,preferably 1, in particular below 0.5, % by weight, based on thedischarge, beforehand. As a rule, the reactor discharge is thereforesubjected to a further polymerization stage before the catalyst isseparated off. The multistage isobutene polymerization described in WO96/40808, in which residual isobutene of the main reactor is consumeddown to about 0.5% in the downstream reactor, is a preferred procedurefor the novel process. Preferably, this second polymerization stage isoperated at the same temperature as the first polymerization stage or ata lower polymerization temperature than the first polymerization stage.As a rule, the temperature difference is from 0 to 20 Kelvin, preferablyfrom 0 to 10 Kelvin.

The downstream reaction, in particular the cooled downstream reaction,results in more complex separating out. The solubility of the complexdecreases at least by a power of 10, and in particular if thetemperature reduction is also effected. Here, the catalyst is obtainedin the form of finely divided droplets, which as a rule are rapidlytransformed into a coherent phase. The complex droplets or the coherentphase have or has a substantially high density than the polymersolution. As a rule, they can therefore be separated from thepolymer-rich, catalyst-poor product phase with the aid of precipitators,separators or other collecting containers. If the catalyst is obtainedonly in the form of very finely divided droplets which are difficult toseparate off, the conventional measures for droplet enlargement, forexample coalescing filters, can be used. Methods for this purpose aredescribed, for example, in WO 99/31151.

The formation of a coherent catalyst phase is however not essential forrecycling the catalyst. A phase in which the complex is stilldistributed in disperse form can, if required, also be fed to thereactor. The concentrated and/or isolated catalyst is then fed to thepolymerization as a rule without further purification or, in the case ofa multistage polymerization, as a rule to the first polymerizationstage. Since as a rule there are certain reductions in activity onisolating the catalyst, said reductions are compensated by adding smallamounts of catalyst, for example from 1 to 30, preferably from 3 to 20,in particular from 5 to 10, % by weight, based on the amounts of complexwhich are required in a straight path. As a rule, it is thereforepossible to recycle from 40 to 95%, preferably from 70 to 90%, of thecatalyst.

The polymer-rich product phase separated off is generally homogeneousand contains only small amounts of soluble catalyst fractions. These aredeactivated in the manner described above, preferably with water.Thereafter, the solvent is separated from the product in the mannerdescribed above and is subjected to the novel wash. In this embodiment,it is also possible to absorb the residues of the dissolved complex onnitrile-containing materials, for example according to EP-A-791 557, ornitrile-modified silica gel.

The novel process enables good control of the isobutene polymerizationand permits specific preparation of highly reactive polyisobuteneshaving a number-average molecular weight M_(n) of from 500 to 50,000Dalton and containing at least 60 mol % of terminal vinylidene groups.The novel process has proven particularly useful in the preparation ofpolyisobutenes having a number-average molecular weight M_(n) of from500 to 5,000, in particular from 700 to 2,500, and containing at least80 mol %, based on all terminal groups, of vinylidene groups. At thesame time, a better molecular uniformity of the polyisobutene,characterized by the ratio of weight average molecular weight {overscore(M)}_(w) to number average molecular weight M_(n) (=dispersityD=M_(w)/M_(n)), is achieved. Typically, the novel process enablesproduction of polyisobutenes in the stated molecular weight range withan M_(w)/M_(n)≦2.5, preferably≦2.0, and in particular≦1.8. In contrastto the prior art processes, these values are also achieved in the caseof solvent recycling. Furthermore, in contrast to the prior artprocesses, the content of reactive terminal groups does not decreasebelow 60, preferably 80, mol % on recycling the solvent. In particular,the process makes it possible to maintain the abovementioned qualityfeatures for polyisobutene having molecular weights of from 500 to5,000. This presumably is due to better control of the polymerization,which has possibly been complicated to date by catalyst traces and/orcocatalyst traces in the recycled solvent.

BRIEF DESCRIPTION OF THE DRAWING

The diagram shown in FIG. 1 is intended to illustrate the inventionwithout restricting it.

FIG. 1 shows a preferred embodiment of a novel process in the form of ablock diagram. The solvent stream (6) recovered by working up bydistillation is subjected to a novel wash with fresh water (10) in awasher W. Fresh solvent (2) is added in M1 to the solvent stream (7)worked up in this manner and thereafter fresh isobutene is added to saidsolvent stream in M2. The stream (9) thus obtained and comprisingsolvent and isobutene is fed to the reactor R. At the same time, thecomplex catalyst (3), optionally in the form of boron trifluoride andcocatalyst, via separate feeds, or in the form of a preformed catalyst,is fed to the reactor. The wash water (11) from the novel water wash Wis added to the reactor discharge (4) in a mixing vessel K fordeactivating the catalyst. The wash water (11 a) is separated off. Theproduct-containing organic phase (5) is subjected to a distillation (D)in which the main amount of the solvent used and any further readilyvolatile components are separated off and are fed as a solvent stream(6) to the novel wash (W). The bottom product (12) of the distillation(D) essentially comprises polyisobutene, which, if required, isfurthermore subjected to extrudate devolatilization at elevatedtemperatures (not shown) for removing sparingly volatile components.

We claim:
 1. A process for the continuous preparation of polyisobuteneby polymerizing isobutene in the presence of a catalyst comprising borontrifluoride and at least one cocatalyst in an inert organic solvent, anda) a part of the reaction mixture obtained thereby being dischargedcontinuously from the polymerization reactor, b) the catalyst beingseparated from the discharge and/or being deactivated in the discharge,and c) the solvent and any unconverted isobutene being distilled offfrom the discharge and recycled to the polymerization reactor, whereinthe distilled-off solvent and, if present, the isobutene are subjectedto a wash with water before the recycling to the polymerization reactorand, Optimally then dried.
 2. A process as claimed in claim 1, whereinthe wash with water is effected in a plurality of stages.
 3. A processas claimed in claim 1, wherein, in the wash with water, thesolvent/water ratio is chosen to be from 1:1 to 1:0.1.
 4. A process asclaimed in claim 1, wherein the discharged amount of reaction mixturecorresponds to a circulation/feed ratio of from 1000:1 to 10:1.
 5. Aprocess as claimed in claim 1, wherein, to remove the catalyst from thedischarge b1) the discharge is separated into a catalyst-enrichedcatalyst phase and into a polyisobutene- and solvent-enriched productphase and b2) the catalyst phase is recycled to the reactor, if requiredafter addition of boron trifluoride and cocatalyst.
 6. A process asclaimed in claim 5, wherein the residual content of isobutene in thedischarge is less than 2% by weight.
 7. A process as claimed in claim 5,wherein the catalyst residues remaining in the discharge after thecatalyst has been separated off are deactivated by adding water.
 8. Aprocess as claimed in claim 1, wherein the wash water produced duringwashing of the solvent is used to deactivate and/or extract the catalystin the reaction discharge.
 9. A process as claimed in claim 1, whereinthe polyisobutene is a highly reactive polyisobutene having an averagemolecular weight M_(n) of from 500 to 5,000 Dalton and containing morethan 80 mol % of terminal double bonds.